ServiceLoader

findFirst

fun findFirst(): Optional<S>!

Load the first available service provider of this loader's service. This convenience method is equivalent to invoking the iterator() method and obtaining the first element. It therefore returns the first element from the provider cache if possible, it otherwise attempts to load and instantiate the first provider.

The following example loads the first available service provider. If no service providers are located then it uses a default implementation.

<code>CodecFactory factory = ServiceLoader.load(CodecFactory.class)
                                         .findFirst()
                                         .orElse(DEFAULT_CODECSET_FACTORY);
  </code>

iterator

fun iterator(): MutableIterator<S>

Returns an iterator to lazily load and instantiate the available providers of this loader's service.

To achieve laziness the actual work of locating and instantiating providers is done by the iterator itself. Its hasNext and next methods can therefore throw a ServiceConfigurationError for any of the reasons specified in the Errors section above. To write robust code it is only necessary to catch ServiceConfigurationError when using the iterator. If an error is thrown then subsequent invocations of the iterator will make a best effort to locate and instantiate the next available provider, but in general such recovery cannot be guaranteed.

Caching: The iterator returned by this method first yields all of the elements of the provider cache, in the order that they were loaded. It then lazily loads and instantiates any remaining service providers, adding each one to the cache in turn. If this loader's provider caches are cleared by invoking the reload method then existing iterators for this service loader should be discarded. The hasNext and next methods of the iterator throw if used after the provider cache has been cleared.

The iterator returned by this method does not support removal. Invoking its remove method will cause an UnsupportedOperationException to be thrown.

load

static fun <S : Any!> load(
    service: Class<S>!, 
    loader: ClassLoader!
): ServiceLoader<S>!

Creates a new service loader for the given service. The service loader uses the given class loader as the starting point to locate service providers for the service.

load

static fun <S : Any!> load(service: Class<S>!): ServiceLoader<S>!

Creates a new service loader for the given service type, using the current thread's context class loader.

An invocation of this convenience method of the form

<code>ServiceLoader.load(service)
  </code>

<code>ServiceLoader.load(service, Thread.currentThread().getContextClassLoader())
  </code>

loadInstalled

static fun <S : Any!> loadInstalled(service: Class<S>!): ServiceLoader<S>!

Creates a new service loader for the given service type, using the extension class loader.

This convenience method simply locates the extension class loader, call it extClassLoader, and then returns

<code>ServiceLoader.load(service, extClassLoader)
  </code>

This method is intended for use when only installed providers are desired. The resulting service will only find and load providers that have been installed into the current Java virtual machine.

reload

fun reload(): Unit

Clear this loader's provider cache so that all providers will be reloaded.

After invoking this method, subsequent invocations of the iterator or stream methods will lazily locate providers (and instantiate in the case of iterator) from scratch, just as is done by a newly-created service loader.

This method is intended for use in situations in which new service providers can be installed into a running Java virtual machine.

stream

fun stream(): Stream<ServiceLoader.Provider<S>!>!

Returns a stream to lazily load available providers of this loader's service. The stream elements are of type Provider, the Provider's get method must be invoked to get or instantiate the provider.

To achieve laziness the actual work of locating providers is done when processing the stream. If a service provider cannot be loaded for any of the reasons specified in the Errors section above then ServiceConfigurationError is thrown by whatever method caused the service provider to be loaded.

Caching: When processing the stream then providers that were previously loaded by stream operations are processed first, in load order. It then lazily loads any remaining service providers. If this loader's provider caches are cleared by invoking the reload method then existing streams for this service loader should be discarded. The returned stream's source spliterator is fail-fast and will throw ConcurrentModificationException if the provider cache has been cleared.

The following examples demonstrate usage. The first example creates a stream of CodecFactory objects, the second example is the same except that it sorts the providers by provider class name (and so locate all providers).

<code>Stream&lt;CodecFactory&gt; providers = ServiceLoader.load(CodecFactory.class)
             .stream()
             .map(Provider::get);
 
     Stream&lt;CodecFactory&gt; providers = ServiceLoader.load(CodecFactory.class)
             .stream()
             .sorted(Comparator.comparing(p -&gt; p.type().getName()))
             .map(Provider::get);
  </code>

toString

fun toString(): String

Returns a string describing this service.